I also see this. I also note that Xorg memory use ramps over a couple of days from 600MB to 1.3G.
Then the desktop becomes unusable, and a reboot is required.
I have tried numerous configurations and tweaks via nvidia-settings, to no avail.

The stock kernel (as opposed to desktop kernel) suffers from the same problem.

Please advise what information can I provide to help debug this - I really want this fixed since the interface is so nice to use after rebooting, but I thought regular reboots were not needed for linux!